Get Your Dog Care Questions Answered by Experts
If she has been boarded at a kennel recently, it could be kennel cough, a common respiratory illness that is highly contagious. Even if animals have been vaccinated, they will still get it if they are exposed.
Aside from that, tracheal problems and heart problems can also cause coughing, as can a general virus.
Any time that I hear of an older dog coughing, I immediately think of a heart problem, especially if the dog is not on heartworm prevention.
You should be pretty concerned. I think that you should make an appointment with your vet as soon as you are able.
Rapid breathing can often be caused by some kind of stress. You should evaluate the situation and see if there are any new stresses.
Obstructions of the nose, tracheal problems and laryngeal problems can also cause increased (or seem to cause) increased respiration.
If your dog is not on heartworm prevention, he might be showing clinical signs of heartworm disease or other heart problem.
If it continues, you need to see your vet as soon as you can.
Let me know if you still have questions.